spraaue



2 SheetsSheet 1.

(No Model.)

I F. J. SPRAGUE.

ADJUSTABLE RESISTANCE FOR ELECTRICAL CIRCUITS. No. 309,167.

Patented Dec. 9, 1884.

INVENTOR:

(No Model.) 2 Sheets-Sheet 2.

F. J. SPRAGUE. ADJUSTABLE RESISTANCE FOR ELECTRICAL CIRCUITS. No. 309,167. Patented Dec. 9, 1884.

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Hill IIIH NH HHI OHH INN H"! 'H" UNITED STATES PATENT OFFICE.

FRANK J. SPRAGUE, OF NEXV YORK, N. Y., ASSIG-NOR TO SAMUEL INSULL,

' TRUSTEE.

ADJUSTABLE RESISTANCE FOR ELECTRICAL CIRCUITS.

SPECIFICATION forming part of Letters Patent No. 309,167, dated December 9, 1884.

Application filed April 3, 1881.

To all whom it may concern:

Be it known that I, FRANK J. SPRAGUE, of New York, in the county and State of New York, have invented a certain new and useful Improvement in Adjustable Resistances for Electrical Oircuits, of which the following is a specification.

The object of my invention is to provide an adjustable resistance of compact and conven- IO ient form, in which there shall be very little metal not in use at any time, variations of resistance being produced by the different combinations into which a small number of coils are thrown by the movement of the adjusting 1 devices.

My invention consists in the novel devices and combinations of devices employed by me in accomplishing the above-named object, as will be hereinafter specified.

The invention is illustrated in the accompanying drawings, in which Figure l is a side view of the resistance-box with the switch boards in section; Fig. 2, a front elevation of the same; Fig. 3, a larger vertical section of 2 one of the resistance-controlling arms; Fig. 4,

a diagram of the switch-boards, resistancecoils, and connections; and Fig. 5a top view of the resistance-coils with the connections in diagram.

My invention is not confined, of course, to the exact number and arrangement of resistance-coils and contact-plates shown and described. These are, however, such as I have found convenient in practice.

A is a wooden frame or box, in which are supported, preferably in a vertical position, twenty-four coils, B, of iron or other wire, of such conducting capacity as may be desired for the particular situation in which the ap- 40 paratus is to be placed.

Upon the top of the box or frame A are two wooden switch-boards, O and G, united by the cross-pieces D D.

Upon switch-board O are contacts a a, etc.

40 Upon board O are contacts I) b, &c. These contacts are forked metal pieces, the contact being made by forcing a metal plate between the forked portions. The contact-arms one for each switch-board-are carried by the shaft or spindle E, which passes through the two boards. Only one of these arms is shown (X0 model.)

in Fig. 1, and, as they are exactly alike I will describe one of them. An insulating-sleeve,

c, is placed upon the shaft, such sleeve being split, as shown. The sleeve is clamped upon 5 5 the shaft by the metal sleeve (Z, which is secured by nut c. In one direction from sleeve d extends the arm f, which carries contactplate 9, this being adapted to enter between the forked portions of the contacts a or 2) upon the switchboard, fitting therein so as to make a good electrical connection. Opposite the arm f the split and forked metal piece h eX- tends from sleeve (1. All these connected metal parts may be made in one piece, if desired. A metal ring, it, is supported upon each switch-board by pins Z Z, and the metal piece It makes contact with this ring, as shown,

by clasping the ring between its two parts.

It will be seen that as the shaft E is turned the pieces at are constantly in contact with rings k, while the connections of plates 9 with contacts a and b are changed as desired.

The circuit-connections are as follows: Four large conductors, in mm" m extend along the bottom of the supporting box or frame between the coils, and each is brought up vertically at one end and connected to one of the contact-plates, c or b. In Fig. 1 this connection is not shown, the conductorsbeing broken off above the supporting-frame. The other ends of these conductors are free. The lower ends of the resistancecoils are separately connected to the conductors on m, &c. The up per ends of the coils are connected to wires 0 0 0 0 0, which extend along under the top of the frame A, and which are connected with the circuit, as will be presently explained. The coils are connected to these conductors o in sets of three each, so that three coils are 0 in multiple are to one another. Thus three multiple-arc coils form the unit of the resistance, the resistance being varied by changing the number and relation of such units.

One or two or any number of coils might be 9 5 separately connected between conductors 0 and m to form the unitary resistance but I have chosen three as a convenient number.

Now, referring to Fig. at, the sections of coils marked p, &c. each represents one ofthe units of resistance-three coils in multiple are, or such other number in such arrangement as may be selected. The switch-boards are,'for the pnrpose of illustration, laid out side by side. The arrows on the switch-boards show the direc tion of revolution of the contact-arms. Each switch-board is, for convenience of explanation, shown as divided into thirty-eight equal parts upon its circumference.

M M is the conductor of the circuit whose resistance is to be varied. It is broken and connected through rods (1 q with the rings 7.: 7.1 of the switch-boards. Connection 0 from the tops of the resistance-coils extends direct to the conductor M; 0 extends to contacts a and If, 0- to contacts a and b, o to contacts a and If, and 0 to contacts a and b. Uonnections m, m, m, and in from lower ends of coils extend, respectively, to contacts I), I)", I), and If. l.\.rrows r indicating direction of current in the position of the contact-arms shown, the resistance-units are in circuit all in series, there being, as is readily seen, no passage for the eurrent from one part of the conductor to the other, except by 0, all the coils 7 o, and I1, is, and 1 upon switch board 0. Now, if it is desired to cut out resistance from the circuit, by turning wheel \V the contact-arms are moved .in directions indicated by the arrows. A movement of one of the thirty-eight divisionsbrings the right-hand arm upon contact 1) without changing the connection of the other arm. All the coils on the right of a will then be short-cireuited and the resistance halved. The next change is produced by moving six divisions, which brings the left -hand arm upon contact a, and right-hand arm off of Z). This divides the resistance into two halves, coils ay/,1), and p being multiple-arced upon p, p, and p It is unnecessary to follow out all the movements in detail. The coils are brought through diltbrcnt combinations of multiple are and series, or are cut out of circuit as occasion requires. At the termination of the movement the lefthand arm is upon a, a, a, and a and the right upon I) and t".

' The resistance is thus entirely shortcircuited.

By this arrangement of contacts the greatest changes of resistance occur when a large resistance is in circuit, and the extent of the changes becomes less as the whole resistance t t t l i i t in circuit becomes less. It is thus well adapted for use with the fouling-circuits of electrical-distribution systems, the greatest resist ance being in circuit when only a few lights are on, and when the addition of one or two lights makes a great change in the whole resistance of the circuit. The division of the contacts between two switch-boards, with the resistance-coils connected between them, makes the apparatus much more compact, as a very large switch-board would be necessary if all. the contacts were placed upon one.

'What I claim is- 1. In an adjustable resistance, the combina tion oftwoseries of metallic contacts, resistance-coils connected between them, and a circuit-controlling arm tor each series, substantially as set forth.

2. The combination of the two switclrboards, each having a circular series of contacts, the resistancecoils connected between them, the revolving contaet-armsone for each switchboardand the common shaft for revolving them, substantially as set forth.

3. The combinationofthe two switchboards, each having a series of contacts, the resistance coils connected between them, and a conncction from one end of the series of coils direct to the circuit, whereby all, the coils may be placed directly in circuit, substantially as set forth.

4-. The combination ofthe two switchboards, each having a series of contacts, the resistancecoils connected between them, and a connection between them independent of the coils, whereby said coils may be short-circnited, sub stantially as set forth.

5. The combination of thebox or frame sup porting the resistance-coils, the two switchboards placed back to back upon said frame, and the shaft passing through both switchboards and carrying a contact-arm. for each, substantially as set forth.

This specification signed and witnessed this 19th day of March, 18st.

FRANK J. SPRAGUE.

\Yitnesscs:

H. \V. SEELY, T. G. GREENE, Jr. 

